A disc-shaped magnetic record medium is known which is commonly referred to as a floppy disc, and a floppy disc drive unit is also known which permits information to be recorded on or retrieved from the floppy disc.
The floppy disc is formed with a plurality of concentric tracks which serve as information record areas. When reading or writing such information, the floppy disc is mounted on the drive unit, and the read/write head is fed through a given distance from a home or reference position on the unit.
A satisfactory recording and playback of information is obviously possible only when the read/write head is located properly relative to a desired track. As is well recognized, a floppy disc comprises a thin disc formed of a synthetic resin, which is susceptible to thermal deformation and deflection. For this reason, there may sometimes be an offset, though small in quantity, between the stop position of the read/write head and the location of a track on which desired information is recorded if the floppy disc is flexed when it is mounted on the drive unit as a result of the thermal deformation or if the access of the read/write head produces a positional error. This results makes it difficult to achieve a satisfactory information recording or playback.
A conventional head feed device is designed to feed the head a given stroke before it is stopped, assuming that a floppy disc is free from any deformation or deflection and is mounted on the unit in an ideal manner. Consequently, if the floppy disc itself has been deformed or flexed to cause a departure, it is evident that an offset is produced between the head and the track. Also the read/write head itself may be stopped at a position which varies from time to time. Thus, there is a need of some means which assures a proper alignment of the read/write head and the track.